1. Field of the Invention
The present invention relates to a circuit substrate in which high-density mounting can be realized by integrally sandwiching a flexible wiring board with two rigid substrates.
2. Description of the Related Art
Cited Patent Reference 1, for example, describes an example of this kind of circuit substrate. The Cited Patent Reference 1 describes a method of manufacturing a printed circuit wiring board in which a flexible substrate is sandwiched by rigid substrates. A method of manufacturing a printed circuit wiring board described in the Cited Patent Reference 1 includes a rigid substrate forming process for forming a rigid substrate in which a first wiring pattern is formed on at least one surface by a patterning process, a flexible substrate forming process for forming a flexible substrate in which a second wiring pattern is formed on at least one surface by a patterning process, a laminating process for integrally laminating the flexible substrate and the rigid substrates by sandwiching the flexible substrate with a plurality of rigid substrates, an abrasive grains abrasion mask forming process for forming an abrasive grains abrasion mask with predetermined portions opened on the rigid substrates which become outer layer substrates and an abrasive grains abrasion process for removing the rigid substrates by effecting the abrasive grains abrasion process on the predetermined regions opened on the abrasive grains abrasion mask to thereby expose the flexible substrate to the outside.
According to the printed circuit wiring board manufacturing method having the above-mentioned arrangement described in the Cited Patent Reference 1, since the flexible substrate with flexibility is manufactured in the state in which the flexible substrate is sandwiched by the rigid substrates, a dam need not be formed near the opening of the rigid substrate, manufacturing efficiency can be improved and a cost can be decreased.
[Cited Patent Reference 1]: Japanese Published Patent Application No. 2004-31682
However, in the case of the related-art circuit substrate manufactured by the aforementioned printed circuit wiring method, once the rigid flexible substrate is integrally molded by sandwiching the flexible substrate with the two rigid substrates. After that, the circuit substrate in which a plurality of rigid substrates is integrally formed with one flexible substrate is formed by removing unnecessary portions of the two rigid substrates. For this reason, since a large number of processes are required until the final circuit substrate is manufactured, a large number of processes cause the manufacturing process to become complex and hence it is unavoidable that the circuit substrate should be manufactured expensively.